Carbonylic-Carbon-Centered Mechanism for Catalytic α-Methylation

Wu, Zeyu; Li, Longfei; Wan, Li; Lu, Xuena; Xie, Yaoming; Schaefer, Henry F.

doi:10.1021/acs.organomet.1c00150

Cited by 6 publications

(5 citation statements)

References 61 publications

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“…The second cycle partially follows the mechanism proposed by Schaeffer and co-workers . As mentioned previously (vide supra), at the initial stages of the reaction, the base plays no crucial role in the dehydrogenation of methanol which contrasts with their findings.…”

Section: Results and Discussionsupporting

confidence: 66%

“…Because complex 3 is an active catalyst, it enabled us to investigate whether the hydrogenation of the α,β-unsaturated ketone intermediate is dependent on a base. Recently, computational studies have shown that in manganese tricarbonyl complexes, the axial carbonyl ligand serves as the catalytic center in conjunction with active participation of the cesium cation of the used base (Cs 2 CO 3 ) . Although during our optimization experiments, we have shown that different bases can be used (Table ), we wanted to know if complex 3 can hydrogenate the intermediate 2-methyl-1-phenylprop-2-en-1-one with the in situ generated hydrogen.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Recently, computational studies have shown that in manganese tricarbonyl complexes, the axial carbonyl ligand serves as the catalytic center in conjunction with active participation of the cesium cation of the used base (Cs 2 CO 3 ). 26 Although during our optimization experiments, we have shown that different bases can be used (Table 1), we wanted to know if complex 3 can hydrogenate the intermediate 2-methyl-1-phenylprop-2-en-1-one with the in situ generated hydrogen. Unfortunately, 4m is not detected under these reaction conditions (Scheme 2D).…”

Section: Mechanistic Studiesmentioning

confidence: 99%

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α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PC_NHCP Pincer Complex with Methanol as a C₁ Source

et al. 2022

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Acceptorless alcohol dehydrogenation is a powerful reaction in sustainable synthesis. When combined in a tandem reaction with dehydrogenative coupling or hydrogen borrowing, acceptorless dehydrogenation can be used for the environmentally benign construction of C−C, C−N, and C−O bonds. While many of these reactions rely on using precious metals, in the past decade the use of earth-abundant metals has become more prevalent. If a green and renewable feedstock could be introduced as well, the sustainability of the acceptorless dehydrogenation could further be increased. Methanol would be such a substrate and could serve as a renewable C1 source when used for the methylation of a wide variety of substrates. Herein, we report the efficient manganesecatalyzed α-methylation of ketones and indoles. The manganese catalyst is based on a PC NHC P pincer platform containing a rare central carbene donor. The reaction supports a diverse set of functional groups, occurs at moderate temperatures (110 °C), and provides the corresponding methylated ketones and indoles in excellent yields. In contrast to previously reported mechanisms, the herein reported mechanism does not depend on metal−ligand cooperativity but rather proceeds via (i) a metal-based mechanism featuring a manganese hydride or (ii) via a ligand-centered mechanism where a manganese-carbonyl acts as catalytic center, depending on the used additive.

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Section: Results and Discussionsupporting

confidence: 66%

Section: Results and Discussionmentioning

confidence: 99%

Section: Mechanistic Studiesmentioning

confidence: 99%

See 1 more Smart Citation

α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PC_NHCP Pincer Complex with Methanol as a C₁ Source

et al. 2022

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“…In accordance with our previous theoretical studies on homogeneous catalytic reactions, − all computations in this study were carried out by the density functional theory method with ωB97X-D functional using the Gaussian 09 program . Geometries were optimized in the 1,4-dioxane solvent using the BS-I basis sets, where the 6-311G(d,p) basis sets were used for nonmetal atoms and the SDD basis sets with effective core potentials were used for metal atoms. , The single-point energy refinements were further performed with BS-II basis sets, where the 6-311++G(2d,p) basis sets were used for nonmetal atoms, and the SDD basis sets were used for metal atoms.…”

Section: Methodsmentioning

confidence: 99%

Unveiling Pre-Transmetalation Intermediates in Base-Free Suzuki–Miyaura Cross-Couplings: A Computational Study

Xie,

Zhang,

Song

et al. 2024

Inorg. Chem.

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The pre-transmetalation intermediates are critically important in Suzuki−Miyaura cross-coupling (SMC) reactions and have become a hot spot of the current research. However, the pretransmetalation intermediates under base-free conditions have not been clear. Herein, a comprehensive theoretical study is performed on the base-free Pd-catalyzed desulfonative SMC reaction. The fragile coordination feature and the acceleration role of the RuPhos chelate ligand are revealed. The hydrogen-bond complex between the Pd−F complex and aryl boronic acid is identified as an important pre-transmetalation intermediate, which increases the energy span to 32.5 kcal/mol. The controlling factor for the formation of the hydrogen-bond complexes is attributed to the electronegativities of halogen atoms in the metal halide complexes. What is more, other reported SMC reaction systems involving metal halide complexes and aryl boronic acids are reconsidered and suggest that the hydrogen-bond complexes widely exist as stable pre-transmetalation intermediates with influencing the catalytic activities. The earth-abundant Ni-catalyzed desulfonative SMC reaction is further designed and predicted to have a higher activity than the original Pd-catalyzed SMC reaction.

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“…In accordance with our previous theoretical studies, − this research was carried out with the DFT ωB97X-D method using the Gaussian 09 program . Geometries were optimized in the THF solvent using the def2-SVP basis sets. , The single-point energy refinements were further performed with the def2-TZVPP basis sets. , Thermal corrections and entropy contributions to the Gibbs free energies were obtained with the ωB97X-D/def2-SVP method.…”

Section: Methodsmentioning

confidence: 99%

Theoretical Study on the Hydrogenolysis of Polyurethanes to Improve the Catalytic Activities

et al. 2022

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The metal-catalyzed hydrogenolysis of polymers is important in waste recycling; however, it is limited by the harsh reaction conditions and the low activities of catalysts, especially for earth-abundant metal-based catalysts. Herein, we perform a comprehensive study on the hydrogenolysis of polyurethane model catalyzed by Fe-, Mn-, Ru-, and Ir-iPrMACHO pincer complexes and propose a cascade mechanism comprising two-level hydrogenolysis and the hydrogenation of formaldehyde. In addition, the substrates and ligands are modulated to improve the activities of chemical recycling to monomer. It is found that the pincer ligands could dissociate from the metal centers at high reaction temperatures and further result in the deactivation of catalysts. The rigid Fe and Mn catalysts with tetradentate cyclic ligands are designed following the guidance, and the computations suggest that those designed catalysts could have high stabilities and activities.

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Carbonylic-Carbon-Centered Mechanism for Catalytic α-Methylation

Cited by 6 publications

References 61 publications

α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PC_NHCP Pincer Complex with Methanol as a C₁ Source

α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PC_NHCP Pincer Complex with Methanol as a C₁ Source

Unveiling Pre-Transmetalation Intermediates in Base-Free Suzuki–Miyaura Cross-Couplings: A Computational Study

Theoretical Study on the Hydrogenolysis of Polyurethanes to Improve the Catalytic Activities

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Carbonylic-Carbon-Centered Mechanism for Catalytic α-Methylation

Cited by 6 publications

References 61 publications

α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PCNHCP Pincer Complex with Methanol as a C1 Source

α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PCNHCP Pincer Complex with Methanol as a C1 Source

Unveiling Pre-Transmetalation Intermediates in Base-Free Suzuki–Miyaura Cross-Couplings: A Computational Study

Theoretical Study on the Hydrogenolysis of Polyurethanes to Improve the Catalytic Activities

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Product

Resources

About

α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PC_NHCP Pincer Complex with Methanol as a C₁ Source

α-Methylation of Ketones and Indoles Catalyzed by a Manganese(I) PC_NHCP Pincer Complex with Methanol as a C₁ Source